Optical and Magnetic Techniques are employed in conjunction with chemical methods in an effort to delineate the structure and function of certain electron transfer proteins. The systems under investigation are the plant and bacterial ferredoxins, high potential iron proteins, metal free and metallo-flavoproteins, hemeproteins and superoxide dismutases. BIBLIOGRAPHIC REFERENCES: K. L. Schepler, W. R. Dunham, R. H. Sands, J. A. Fee, and R. H. Abeles, A Physical Explanation of the EPR Spectrum Observed During Catalysis by Enzymes Utilizing Coenzyme B12, Biochimica et Biophysica Acta 397 (1975) 510-518.